The present invention relates to clarifiers of a type wherein inclined flow passages are formed by a plurality of parallel, spaced apart plates and more particularly to such clarifiers wherein liquid to be clarified flows generally vertically through the inclined flow passages.
Various types of clarifiers have been developed for use in place of large settling basins, tanks or the like where liquid is held over prolonged periods of time until clarification occurs because of normal sedimentation and phase separation phenomena. Inclined plate clarifiers have been found to be particularly effective in such applications, particularly in industrial and municipal water treatment facilities, because of increasingly rigid requirements for high effluent quality.
Inclined plate clarifiers are commonly characterized by a number of inclined flow passages formed by parallel, spaced apart plates. The concept of employing a series of inclined passages in close proximity to each other has been found to be particularly effective since the settling area per unit volume is greatly increased while, at the same time, the overall size and cost for the clarifier or settling unit may be reduced.
Within an inclined plate clarifier, liquid to be clarified flows along the flow passages between the plates and is subject to phase separation or the settling of solids under conventional principles of operation. Inclined plate clarifiers may generally be divided into classes adapted respectively for generally vertical flow or for cross-flow where liquid to be clarified flow generally horizontally through the flow passages. Vertical flow clarifiers may be adapted for operation either in an "upflow" and/or "downflow" mode of operation with relatively heavy and/or light phase material being removed as the liquid flows along the inclined passages.
The present invention particularly contemplates a vertical flow clarifier in which liquid to be clarified flows generally vertically through the inclined flow passages formed by the spaced apart plates. Thus, inlet and outlet means for the clarifier are in communication with the flow passages generally adjacent their inclined ends.
It is often a particular problem to uniformly distribute influent liquid across each of the flow passages in vertical flow clarifiers. Without such uniform distribution, excessive settling may tend to occur within portions of the flow passages and may even result in settled solids tending to block or plug the flow passages. A related problem involves solids which initially settle while the liquid is being introduced into the flow passages. Buildup of these initially settled solids may also tend to cause undesirable blockage. Accordingly, it is particularly important to assure that any such initially settled solids may pass into a suitable sediment chamber and are not allowed to remain in the flow passages.
It is also particularly desirable to adapt such clarifiers for operation under widely varying conditions. For example, in some applications, liquids to be clarified may have varying amounts of suspended solids ranging from heavy material tending to settle out very rapidly to light material which is difficult to separate and may in some instances require the use of flocculating agents. Liquids to be clarified may also require the removal of a relatively low density phase such as oils suspended in water. The liquid may also be either aqueous or non-aqueous and, in some instances, may include both solids subject to settling under the effects of gravity as well as one or more low density phases which must be separated in order to produce a clarified liquid of satisfactory quality.
In summary, various clarifiers in the prior art have demonstrated an ability to operate satisfactorily in selected applications. However, a need has been found to remain for a vertical flow clarifier which is adaptable to a variety of operating conditions and which may be employed to produce a high quality effluent.